This may actually be more of a media question I suppose. It says the 4mm tapes hold 20gb/40gb. IT Backup exec media properties says my total capacity is 19gb and that bytes written is 26gb, is that due to compression? How do I know when my data is exceeding the tape space, when I get over 40gb? Can someone clarify?
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9.1 Backup media question 1
- Thread starter kevotron
- Start date
The 40gig is rated on purely text files. The rule of thumb is half the difference is considered great real-world compression. So the 19gigs or 20 is the navtive capacity.
30gig on a tape would be considered good compression. The tape drive does the compression and backup exec doesnt unless you choose software compression. Make sure you on the latest SCSI Drivers/Firmware and Veritas Drivers / Tape drive firmware. It may make a little difference. If you backing up database files. pictures or files that are already compressed then the tape drive is not going to due much more.
30gig on a tape would be considered good compression. The tape drive does the compression and backup exec doesnt unless you choose software compression. Make sure you on the latest SCSI Drivers/Firmware and Veritas Drivers / Tape drive firmware. It may make a little difference. If you backing up database files. pictures or files that are already compressed then the tape drive is not going to due much more.
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As stated above, the first figure is the native capacity, the second is with compresison. Typically you can expect from 1.5:1 to 1.7:1 compression ratios. If you are backing up highly repetitive data or data that is mostly text (which is by definition repetitive) you can get 2:1 or higher compression ratios.
If you are backing up an entire server, it is extremely unlikely that you will get 2:1 compression because you have a mix of binaries, text files, and compressed files (which includes most image file formats).
How do you know when you're running out of space? It's a bit of a guess really. If it is 20/40 then you'll probably run out of space around 30, depending on the compression ratios. Your best bet is to monitor the size of the backups to see how much tape you are using each backup (roughly), and then estimate how many you will be able to get on a tape.
If you are backing up an entire server, it is extremely unlikely that you will get 2:1 compression because you have a mix of binaries, text files, and compressed files (which includes most image file formats).
How do you know when you're running out of space? It's a bit of a guess really. If it is 20/40 then you'll probably run out of space around 30, depending on the compression ratios. Your best bet is to monitor the size of the backups to see how much tape you are using each backup (roughly), and then estimate how many you will be able to get on a tape.
- Thread starter
- #4
I am averaging about 1.20:1 -- It is a manufacturing environment with a lot of word, excel, and cad drawings--also a ERP database. So on the 20/40s with 26GB written and 1.20:1 compression ratio, I will probably max out at 30GB--what then? What is my recourse? Do I have to buy another drive that can handle a larger capacity? It is pretty much a given at some point we will go over 30GB.
Well, if it's a 20 GB cartridge and you're averaging 1.2:1 compression, you'll probably max out at around 24 GB, not 30 GB.
Are you backing up 20 GB in a single backup? If so, then your answer will be to either move to multiple drives, a larger drive, or an autoloader. Or you could always go to multiple tapes using the single drive, but then you have to change the tapes manually.
Where I work we started with 3 Ultrium 100/200 drives. After 2 years we're up to 5. The problem with backing up large data sets is that it takes a long time. We decided in our environment that we were better off with 5 drives backing up in parallel than we would be with 1 or 2 larger capacity drives. Before we added the 2 additional drives our backup windows were running about 12 hours long (for the longest of the 3 backups), now they're down to about 4-5 hours each.
Are you backing up 20 GB in a single backup? If so, then your answer will be to either move to multiple drives, a larger drive, or an autoloader. Or you could always go to multiple tapes using the single drive, but then you have to change the tapes manually.
Where I work we started with 3 Ultrium 100/200 drives. After 2 years we're up to 5. The problem with backing up large data sets is that it takes a long time. We decided in our environment that we were better off with 5 drives backing up in parallel than we would be with 1 or 2 larger capacity drives. Before we added the 2 additional drives our backup windows were running about 12 hours long (for the longest of the 3 backups), now they're down to about 4-5 hours each.
- Thread starter
- #6
OK, according to my media properties
Used capacity: 18.4GB
Available Capacity: 719MB
Total Capacity 19.1GB
Bytes written 26.4GB
Compression Ratio 1.43:1
So if I am following correctly, that 719MB is all I have left, and as it fills ot it will be more than 719MB due to compression, so kind of calculate 719MB and the cmopression ratio and thats how much space I will have left on the media? So I would have around a Gig or so left before my tapes are running out? Am I understanding correctly? Also , can I ask, if I purchase a second drive and backup in parallel--how would that work, do I buy the exact same drive and then configure that in Veritas? I am not sure how parallel backusp work, our backup windows is pretty much 12 hours, would buying a bigger drive be easier? What would you recommend? Sorry about all the questions. I really appreciate the help!
Used capacity: 18.4GB
Available Capacity: 719MB
Total Capacity 19.1GB
Bytes written 26.4GB
Compression Ratio 1.43:1
So if I am following correctly, that 719MB is all I have left, and as it fills ot it will be more than 719MB due to compression, so kind of calculate 719MB and the cmopression ratio and thats how much space I will have left on the media? So I would have around a Gig or so left before my tapes are running out? Am I understanding correctly? Also , can I ask, if I purchase a second drive and backup in parallel--how would that work, do I buy the exact same drive and then configure that in Veritas? I am not sure how parallel backusp work, our backup windows is pretty much 12 hours, would buying a bigger drive be easier? What would you recommend? Sorry about all the questions. I really appreciate the help!
Looks like you're getting about 1.4:1 compression. That 719 MB remaining is actual native capacity, not compressed. You're looking at roughly 1 GB of compressed capacity left.
The way we do parallel backups is have multiple servers running Backup Exec, each with it's own drive.
The way we do parallel backups is have multiple servers running Backup Exec, each with it's own drive.
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